Put your hazard suits on, folks!
It's obvious that I got carried away by my imagination, when I wrote this subheading, but if the same wasn't true for the author of the repeatedly cited press release, many of us are about to suffer the consequences of the potential unsafety of the hitherto unknown sucralose metabolites in our guts, pretty soon.

This is part III of a multi-part series:

Sucralose, insulin, glucose, GLP-1

Appetite, Obesity & Gut Health

Cancer, Drug & Hormone Interact.

I know that Mark Sisson likes to says this, but this website is not written by a machine, but by a man who has the same "short" 24h days you have... basically, what I am trying to say is that I had to split this review of the review into a "trilogy" - and be honest, you wouldn't want an article thrice as long as this one, would you?

In fact, you don't even have to go searching the databases for hours to find evidence that would support the claim that some of these metabolits that supposedly arise, while sucralose passes through our digestive tract (hitherto we have only highly debated evidence from rodent studies that there are any metabolits at all, by the way) could be pretty nasty bastards. In their 2008 paper, Abou-Donia et al. (2008), whose rodent study is still the only one to support the claim that the consumption of sucralose (HED 42mg/day or more over 3 months) will lead to a "reduction in the number and balance of beneficial bacteria in the gastrointestinal tract" (quote from press release; learn more), cite a study, for example, in which Sasaki et al. (2002) confirmed that sucralose exerts genotoxic effects. This does not mean that the DNA breaks / changes the researchers observed lead to the development of cancer, but the in vivo comet essay the researchers used, is generally considered a very reliable indicator of the genotoxicity of the tested compound in a particular body part (Brendler-Schwaab. 2005).

Believe it or not, but aspartame is one out of three sweeteners Sasaki et al. tested that are not genotoxic | more about aspartame

It's not just sucralose: I guess it's only fair, if I point out that Sasaki's study showed that sodium cyclamate, saccharin, sodium saccharin, likewise artificial sweeteners, caused DNA damage to various organs, as well. The dosage that was necessary to trigger these effects was yet unrealistically high: 2000mg/kg for sucralose and sodium cyclamate, 1000mg/kg for saccharin and sodium saccharin - for humans that would be 26g and 13g of pure sweetener every day! Ah, before I forget to mention that: Acesulfame-K, aspartame and stevia were also tested and found to be benign.

The absence of direct evidence of real-world negative effects, the insignificance of the long-demonstrated weak muatgenicity in the mouse lymphoma mutation assay, both, the WHO and the FDA have confirm ed in independent reports (WHO, 1989; U.S. FDA, 1998), is thus probably the reason the compound has still been approved as a food additive in 1991 - initially in Canada and Australia, then in the rest of the federally regulated world (Canada & Australia, 1993; New Zealand, 1996; US, 1998; EU, 2004). Today, the sales in sucralose alone account for 27.9% of the $1.146 billion global highpotency sweetener market (Leatherhead Food Research, 2011). No wonder, after all, sucralose is utilized in thousands of food, beverage, and pharmaceutical products in North America, Latin America, Europe, the Middle East, and the Asia-Pacific region (Schiffman. 2013).

So what does the (almost) "real-world" evidence say?

It's unquestionably debatable whether this was a good idea or a tragic mistake, but without corresponding "real-world" assays from longer-term rodent studies, the damage that occurs in response to the DNA breaks that have been observed in in-vitro studies may well be so small that the DNA repair machinery that operates in our bodies 24/7 can fix it easily. In this case, our coroners would probably find a similar increase in non-neoplastic findings (=non-cancerous, often minimal tissue growth, where it does not belong), as they were reported by Mann et al. (see list below the red box) in a combined chronic toxicity/carcinogenicity study of sucralose in Sprague–Dawley rats and a carcinogenicity study of sucralose in mice (Mann. 2000a, 2000b). Direct evidence for the development of cancer and/or the potential epigenetic changes is yet, as Schiffman & Rother have to concede, simply not available.

Sucralose + heat - a potentially hazardous combination: Contrary to often cited claims by Barnd & Jackson (1990) or Miller, et al. (1999), there is more recent evidence that suggest sucralose is not heat stable (Jahn & Yaylayan. 2010; Schiffman. 2012; Schiffman and Abou-Donia. 2012). According to these more recent papers ther are a whole host of thermal degradation products in cookies. Whether these byproducts pose a health risk is however not know for most of them. Only the chloropropanols that form when the reaction occurs in the presence of gylcerol (Rahn. 2010), are well-known genotoxic, carcinogenic, and tumorigenic compounds (Biles. 1983; Cho. 2008; Tritscher. 2004; SCF. 2001; WHO, 2002).

Quite the contrary, if you look at the literature as a whole, there is plenty of data that would support the decision of the Australian, US and EU to approve sucralose as a food additive, e.g.:

No toxic effects even with 3% of total dietary intake in Sprague–Dawley rats; all non-neoplastic findings that occurred were of no toxicological significance and are part of the regular aging process of this strain of rats (Mann. 2000a)

No positive results in in vivo chromosome aberration test in rats and two separate micronucleus tests in mice with doses of up to 2,000mg/kg for 5 days (Brusick. 2010)

No effect on organ and general development, when fed to pregnant rats and rabbits in HEDs of up to 26g (rats) and 9g, respectively (Kille. 2000)

I don't want to discard the existing evidence Schiffman et al. cite in favor of their "sucralose is the devil" hypothesis, but results of the vast majority of these studies can hardly be considered relevant with respect to the question whether the comparatively small amount of sucralose that may be present in your foods, supplements or whatever you may be sweetening with sucralose is going to harm you or your DNA:

The death of one out of 10 mice in a study by Finn and Lord that occured in response to the ingestion of the human equivalent of 1g/day of sucralse can hardly be considered conclusive evidence in favor of the "sucralose is poison hypothesis (Finn. 2000).

The effects Mann et al. describe in a study where 3%-5% of the chow was pure sucralose is devoid of any relevance for our question (Mann. 2000a; Goldsmith. 2000). The same goes for the numerous studies where the lab animals received sucralose in amounts of >500mg/kg body weight (e.g. Finn. 2000; Kille. 2000). For a human being that would be more than 6.5g/day - and that's only if the lab animal was a rodent. For larger animals it would be even more.

Now, you can always argue that the negative studies just weren't long enough to elicit similar effects at lower dosages or, if you prefer that, work yourself up into a lather about the fact that (conspiracy-)theoretical, all the benficial studies could have been openly funded or secretly supported by people / companies with a vested monetary interest in positive safety data. In fact, the existence of a review of the safety of Splenda the lead author of which works for
McNeil Nutritionals, LLC, who market Splenda for Johnson & Johnson (Grotz. 2009), or a "expert panel" review you will read about later in this article actually support that this may be the case, the same can unfortunately be said of almost every food additive - including stevia, by the way.

Let's get on to potential endocrine effects

In view of the fact that it is pointless to speculate about the validity of the data from the positive studies in the foregoing list, I want to turn to another, the final and as we are going to see not necessarily more "productive" topic of this third and last installment of my sucralose review trilogy: The endocrine effects.

Sucralose + Vitamin B12: This is not exactly an endocrine
effect, but in the end it could become one, when large enough quantities
of cobalamine, aka "vitamin B12" react with sucralose in the liver,
vitamin B12 deficiency could be a potential side effect. Aside
from the in-vitro evidence Motwani et al. present in their 2011 paper in Food and Chemical Toxicology,
there is yet no evidence that would suggest that this is actually
happening, let alone to an extent that would leave you B12 deficient like a vegan ;-)

In that, I am using the word "endocrine" in its most general sense, which denotes anything that is produced or directly triggered by an organ and has influence on other organs / tissues or the whole body. The sucralose induced changes in the expression of enzymes from the P450 cytochrome cascade that are responsible for the interconversion / metabolism of all sorts of molecules, including hormones and medications would be one example for such effects.

To this ends we have to go back to the previously cited study by Abou-Donia et al. (2008), of which I did not tell you in the last installment of this series that it has (obviously) been under heavy attack by toxicology experts who do not necessarily doubt the validity of the study data Abou-Donia et al. present, but claim that their interpretation was irresponsible.

A brief note on the criticism of the Abou-Donia study: As you'd expect it's no coincidence that the corresponding paper carries the phrase "expert panel" in it's title. It was after all written and published on request of McNeil Nutritionals, a marketer of
retail products that contain the non-nutritive sweetener, sucralose, who paid the "panel of
experts" to do a "independent and rigorous review of the 2008 study by Abou-Donia et al." (Brusick. 2009)

I won't discuss all the objections the "expert panel" proffers. Not because I think that their general objections against hasty conclusions with respect to unwanted negative health effects weren't justified, but rather because I want to get back to Schiffner's & Rother's review, where you'll find the following comment about the CYP-modifiying effects Abou-Donia et al. observed and Brusick et al.'s criticism:

"The results in Table 1 [identical copy on the right] indicate that the magnitude of elevation for both CYP3A and CYP2D expression increased in a linear, dose-dependent manner as the dosage of sucralose increased from 3.3 to 5.5 to 11 mg/kg/d.

This finding of significant and parallel increases in expression of two different CYP enzymes does not support the claim made by Brusick et al. (2009) that increases in CYP from sucralose ingestion were only normal biological variations."(Schiffman. 2013)

In other words: Coincidental increases in CYP activity would not 'coincidentally' be dose-dependent, as well. If we also remind ourselves of the fact that the human equivalent doses of said 3.3, 5.5 and 11mg/kg sucralose would be (only) 43mg, 71mg and 143mg it is self-evident that we cannot simply ignore the acute and persistent increases in intestinal P-gp, CYP3A, and CYP2D (in humans this is CYP2D6; cf. Laurenzana. 1995) in the jejunum and ileum of About-Donia's hairy subjects.

The obvious question, now, is: Does this even matter?

I mean, changes in the expression of some cryptic enzymes in the gut - who cares? After taking a look a the list of substrates that are enzymatically processed by CYP3A, alone, even the small 44% increase that occured in response to the rodent equivalent of 43mg appears relevant.

On this list are some immunosuppressants, many chemotherapeutics including tamoxifen and anastrazole, which are popular with athletes who use PEDs. There are SSRIs, like citalopram, norfluoxetine, sertraline, other anti-depressants like mirtazapine, or
buspirone, the whole list of anti-psychotics, opoids and many analgesics, benzodiazepines, statins like atorvastatin, lovostatin and simvastatin, calcium channel blockers, anti-histamins and even viagra and Co (PDE-5 inhibitors). And even our good old caffeine is on the list of CYP3A4 substrates, on which you'll also find estrogen, testosterone, progesterone, finasteride and torimifene. It's thus not just that your chemotherapy may fail, your depression may return, you may run havoc, hurt all over, increase your cholesterol levels, get high blood pressure, have life-threatening allergic reactions, because your meds are not working properly no (!), even worse caffeine may stop working ;-)

Unlike the increase in CYP2D6 that simply adds to the sucralose ↔ drug interactions, the corresponding increase in P-gp activity and thus the transport of chemicals from gut cells (enterocytes), back into the intestinal lumen could affect the absorption of an even wider range of both wanted and unwanted chemicals / xenobiotics with a hydrophobic and amphiphilic structure.

The net result of the increases in CYP and pGP activity is thus a significant decrease in the concentration of a xenobiotic compound on its way from the gastro-intestinal tract to the liver. Whether this amplified "first pass effect" would actually have physiologically relevant consequences in human beings is yet something we cannot tell without somebody paying for the costly research.

To complicate things, we must not ignore the possibility that "[...t]he rise in CYP expression reported
by Abou-Donia et al. (2008) may result
from 'autoinduction', by which sucralose
enhances it own metabolism." It would thus be a second St. John’s wort, which will also increase its own metabolism by the activation of P-gp and CYP. For Hypericum perforatum extracts, which are often used as mild anti-depressants, we do already know that it affects the metabolism of an endless list of drugs and herbal supplements, and can reduce the levels of 5-alpha reduced androgens like DHT (estrogen and testosterone appear not to be influenced, though; cf. Donovan. 2005).

So what about toxicity and endocrine disruption? If we discard the potential interference with drugs and consequent "St. John's Wort"-esque side effects, I would say that the dosages that are necessary to actively induce more or less insignificant DNA damage in rodent studies, as well as the absence of any evidence of toxic effects from one of the historical single-dose or short-term sucralose studies in humans (Mezitis. 1996; Baird. 2000) make it appear very improbable that the habitual, but reasonable use of sucralose could have toxic or carcinogenic effects.

Remember the Science Round-Up from March? The safety of stevia, is not beyond doubt either | more

The "benefit of the doubt" is yet no acquittal, it is only my assessment of the reasoning Schiffman & Rother provide in their paper, the relevant parts of which are all based on mere hypothesis, e.g. the "IBD ↔ sucralose"-hypothesis by Qin et al. (2011, 2012), or the "there may arise different more toxic sucralose metabolites in the human vs. rat digestion tract"-hypothesis by Goldsmith (2000) and Mann (2000a) and/or rely on data from the highly disputed Abou-Donia study, the most significant result of which are (imho) still the pronounced changes in the gut microbiome (read more in the last episode of this three part series).

At the moment, it does yet still look as if you were on the "safer" side if you prefer stevia sweetened products, although I honestly have my doubts that we wouldn't observe similar effects in mice, rats and all sorts lab critters, if 5%+ of their diet was pure stevia. The dosage makes the poison, you better remember that.

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